We present a detailed experimental and theoretical analysis of the dispersion and non-linear Kerr frequency shifts of plasma modes in a one-dimensional Josephson junction chain containing 500 SQUIDs ...in the regime of weak nonlinearity. The measured low-power dispersion curve agrees perfectly with the theoretical model if we take into account the Kerr renormalisation of the bare frequencies and the long-range nature of the island charge screening by a remote ground plane. We measured the self- and cross-Kerr shifts for the frequencies of the eight lowest modes in the chain. We compare the measured Kerr coefficients with theory and find good agreement.
This article reviews our present understanding of QCD spin physics: the proton spin puzzle and new developments aimed at understanding the transverse structure of the nucleon. We discuss present ...experimental investigations of the nucleon's internal spin structure, the theoretical interpretation of the different measurements and the open questions and challenges for future investigation.
A compact directive dual linear polarized ultra-wideband (UWB) antenna designed for building material analysis (BMA) devices in the frequency range from 2.6 GHz to 4 GHz is proposed. The antenna has ...a total size of 61 mm 2 and a height of 18 mm. The radiation patterns for both polarization directions are symmetrical over a wide bandwidth and radiate perpendicular to the antenna surface. The wave propagation behavior into the wall is investigated and measurement results with different antenna to wall surface distances are presented. The principle of the antenna is described and experimental results show a good performance for building material analysis.
Exclusive electroproduction of \(\omega\) mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of Q\(^2\)>1.0 GeV\(^2\), 3.0 GeV < W < 6.3 GeV, and -t'< 0.2 ...GeV\(^2\). Results on the angular distribution of the \(\omega\) meson, including its decay products, are presented. The data were accumulated with the HERMES forward spectrometer during the 1996-2007 running period using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. The determination of the virtual-photon longitudinal-to-transverse cross-section ratio reveals that a considerable part of the cross section arises from transversely polarized photons. Spin density matrix elements are presented in projections of Q\(^2\) or -t'. Violation of s-channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is found and the phase shift between those amplitudes that describe transverse \(\omega\) production by longitudinal and transverse virtual photons, \(\gamma^{*}_{L} \to \omega_{T}\) and \(\gamma^{*}_{T} \to \omega_{T}\), is determined for the first time. A hierarchy of helicity amplitudes is established, which mainly means that the unnatural-parity-exchange amplitude describing the \(\gamma^*_T \to \omega_T\) transition dominates over the two natural-parity-exchange amplitudes describing the \(\gamma^*_L \to \omega_L\) and \(\gamma^*_T \to \omega_T\) transitions, with the latter two being of similar magnitude. Good agreement is found between the HERMES proton data and results of a pQCD-inspired phenomenological model that includes pion-pole contributions, which are of unnatural parity.
